Hybrid power supply apparatus for battery replacement applications

ABSTRACT

This application relates to a hybrid power supply apparatus comprising a fuel cell and an energy storage device for use in off-road electric vehicles, such as lift trucks. The apparatus is a substitute for conventional lead acid batteries and is sized to fit within a conventional lift truck battery receptacle tray. The fuel cell and fuel processor systems are designed to meet the average load requirements of the vehicle, while the batteries and power control hardware are capable of responding to very high instantaneous load demands. The invention has a similar electrical interface as conventional battery systems and does not require vehicle modification. The apparatus is air-cooled to ensure that the hybrid power components operate within a preferred temperature range and to maintain the external surfaces of the apparatus and exhaust gases within safe temperature limits. Apart from vehicular applications, low power hybrid fuel cell products as exemplified by the present invention may also find application in uninterruptable power supply systems, recreational power, off-grid power generation and other analogous applications.

TECHNICAL FIELD

This application relates to a hybrid power supply apparatus comprising afuel cell and an energy storage device suitable for use in electricoff-road vehicles, such as lift trucks and ground support equipment. Theinvention is a substitute for conventional lead acid batteries and issized to fit within a standard electric vehicle battery receptacle tray.Other low power product applications are also described.

BACKGROUND

Off-road electric vehicles, such as lift trucks, sweepers and scrubbersand ground support equipment, are used in a variety of commercial andrecreational applications. By way of example, electric lift truckscomprising pallet forks are commonly used in retailing, wholesaling andmanufacturing operations for lifting and moving materials insidewarehouses and the like. Since lift trucks are often operated indoors,the use of internal combustion engines is precluded. In most cases lifttrucks are battery powered to avoid potentially harmful emissions. Eachbattery is mounted within an enclosure comprising a battery receptacletray or cavity typically located near the rear of the vehicle (althoughthe location varies depending upon the vehicle model). The batteriestypically include handles or lifting grips and the receptacle tray mayinclude rollers to facilitate battery movement, for example duringrecharging operations. When in use, the battery output is electricallyconnected to the vehicle drive system with a DC interface plug.

Various types of lead acid battery systems are available for use in lifttrucks and other similar electric vehicles. Flooded battery systemsprovide approximately 6-8 hours of operation and require frequentwatering to maintain the chemistries in their cells as they are chargedand discharged. Batteries requiring less frequent watering, such as“Water-less”™ battery systems manufactured by Hawker Powersource, arealso available and provide similar performance to flooded batteries.Recently “maintenance free” battery systems have been introduced whichdo not require any watering, but require more expensive chargers.Maintenance-free systems have a lower energy storage capacity per cubicfoot and therefore provide fewer hours of operation than flooded orreduced water batteries of the same size.

All conventional battery systems designed for low power vehicularapplications suffer from serious shortcomings. A primary limitation isthat conventional batteries must be recharged at frequent intervals,usually at least every 6-8 hours. Accordingly, battery charging stationsmust be provided at the worksite. The establishment of a batterycharging infrastructure is costly and occupies valuable warehouse space.Moreover, the vehicles cannot be continuously operated (i.e. insequential shifts) without routinely swapping discharged and chargedbatteries. This frequent daily removal of discharged batteries andsubstitution of fully charged batteries is labor-intensive andpotentially dangerous (conventional battery enclosure systems for ClassA lift trucks weigh up to 900 pounds). In order to be effective, suchbattery swapping also requires multiple batteries per vehicle whichincreases operating costs.

Conventional batteries must also be serviced at frequent intervals forcleaning and watering. The presence of battery acid poses employeesafety risks and the potential to damage equipment.

Further, conventional battery systems are incapable of operating atoptimum efficiency in many industrial applications. As shown in theTable 1 below, lift trucks typically have a pattern of power usage or“duty cycle” which is characterized by loads which fluctuatesubstantially during the course of a work shift. For example, althoughthe average load across an entire seven hour work shift is less than 1kW, power requirements on the order of 8-10 kW for short durations arerequired at irregular intervals to meet operational demands. The stateof charge of the battery must always be high enough to ensure that thebattery is capable of responding to high current requests by the lifttruck (even though the average power requirement is relatively low).This decreases the effective charge life of the battery, requiringrecharging at more frequent intervals and resulting in operatingdowntimes.

The use of fuel cell power systems in industrial vehicles as analternative to battery power is well known in the prior art. Fuel cellsystems offer many important benefits including extended operatingtunes, low emissions and the flexibility to utilize readily availablefuels, such as methanol and propane (LPG). Further, the need for abattery charging infrastructure as described above is avoided, includingthe need for multiple batteries.

Notwithstanding these advantages, previous attempts by originalequipment manufacturers (OEMs) to integrate fuel cell power systemsemploying conventional fuels into industrial trucks at a reasonable costhave been largely unsuccessful. It is not feasible to adapt existingtrucks to fuel cell power without making extensive truck-levelmodifications. Each OEM brand truck requires a unique integrationapproach which is often difficult and expensive to implement, especiallyfor existing fleets of vehicles. Moreover, if the fuel cell systemfails, the truck must be taken out of service.

The fact that duty cycles for lift trucks and other similar vehicles arecharacterized by very high peak to average load ratios poses particularoperational challenges. Many fuel cell systems employ reformers whichconvert conventional fuels into hydrogen-enriched gas which the fuelcell system transforms into electricity. However, this reforming processis relatively slow which limits the load following capabilities of thefuel cell. Also, in order to maximize the useful life of fuel cellcomponents, it is preferable to operate the fuel cell at near steadystate conditions rather than adopting a load following approach.

Some hybrid power supply systems are known in the prior art for use inapplications subject to sudden load fluctuations. U.S. Pat. No.4,883,724, Yamamoto, issued Nov. 28, 1989 relates to a control unit fora fuel cell generating system which varies the output of the fuel celldepending upon the state of charge of the battery. In particular, aDC/DC converter is connected between the output of the fuel cell and thebattery and is responsive to a control signal produced by a controller.The purpose of the Yamamoto invention is to ensure the storage batteryis charged for recovery within the shortest possible time to reach atarget remaining charge capacity under charging conditions that do notcause deterioration of performance of the battery. When the chargedquantity of the battery is recovered to the target value, the controllerlowers the output of the fuel cell to its normal operating state. In thecase of no external load, such as during extended periods ofinterruption in the operation of the lift truck, the fuel cell iscontrolled to stop after the storage battery is charged.

The primary limitation of the Yamamoto control system is that controlalgorithm is designed for prolonging the useful life of the storagebattery rather than the fuel cell. By varying the fuel cell output tocharge the storage battery for recovery within the shortest possibletime, the long-term performance of the fuel cell is compromised.Moreover, Yamamoto does not disclose a hybrid fuel cell system which isconfigured to fit within a small geometric space.

The need has accordingly arisen for a hybrid architecture specificallyadapted for lift trucks and other low power applications whichintegrates fuel cell technology with conventional battery systems. Inthe present invention the fuel cell and fuel processor systems are sizedto meet the average load requirements of the vehicle, while thebatteries and power control hardware are capable of responding to veryhigh instantaneous load demands. The invention may be substituted forconventional batteries to improve performance without retrofittingexisting fleets of vehicles. As described further below, the applicant'sinvention fits into conventional lift truck battery receptacle trays andhas a similar electrical interface as conventional battery systems.Apart from vehicular applications, low power hybrid fuel cell productsas exemplified by the present invention may also find application inuninterruptable power supply systems, recreational power, off-grid powergeneration and other analogous applications.

SUMMARY OF INVENTION

Conventional traction batteries are removably positionable within abattery receptacle tray of an electric vehicle and include a poweroutput connectable to the vehicle drive system. In accordance with theinvention, a hybrid power supply apparatus is provided which isinterchangeable with such conventional batteries. The apparatus includesa fuel cell; an energy storage device chargeable by the fuel cell; ahousing enclosing the fuel cell and the energy storage device, thehousing being sized to fit within the battery receptacle tray; and apower output electrically connectable to the storage device andextending externally of the housing for electrically coupling theapparatus to the drive system of the vehicle when the housing ispositioned within the battery receptacle tray.

Preferably the apparatus further includes a coolant system for flowinggas through the housing. The coolant system may include a gas inlet fordrawing gas into the housing; at least one blower positioned within thehousing for moving gas through the housing in predetermined flow pathsto regulate the temperature of the apparatus; and a gas outlet forexpelling exhaust gas from the housing. In a particular embodiment ofthe invention, the housing includes a user interface surface which isexposed when the housing is placed within the vehicle receptacle tray.Both the gas inlet and gas outlet are located on the user interfacesurface. The coolant system is configured so that the temperature of theexhaust gas and the user interface surface does not exceed 50° C. whenthe coolant system is in operation.

The apparatus further preferably includes a fuel processor positionedwithin the housing for converting a source of fuel to hydrogen-enrichedgas for delivery to the fuel cell. In one preferred embodiment of theinvention, the fuel processor is a reformer for converting conventionalfuels, such as methanol and propane, to hydrogen gas. The apparatus mayinclude a fuel storage chamber located within the housing which is influid communication with the fuel processor. A fuel inlet may beprovided on the housing, such as on the user interface surface, forsupplying fuel to the fuel storage chamber. In one embodiment, the fuelstorage chamber is thermally isolated from the remainder of the housing.

The apparatus also preferably includes a DC/DC power converterpositioned within the housing for converting the DC current generated bythe fuel cell to a voltage suitable for delivery to the energy storagedevice, which may consist of a battery or capacitor, or to an externalload. A controller may also be mounted within the housing for regulatingoperation of the fuel cell and power converter depending upon the stateof charge of the energy storage device.

The apparatus is designed to closely simulate the weight characteristicsof a conventional traction battery to ensure proper balancing of theelectric vehicle. To this end, one or more load compensators may bepositioned within the housing for increasing the weight of the apparatusto a weight approximating the weight of a conventional battery. Sincefuel cell systems are more sensitive to vibration and shock thanconventional batteries, vibration dampeners may be positioned within orsurrounding a portion of the housing for absorbing vibration when thehousing is within the battery receptacle tray and the vehicle is inoperation. Preferably the apparatus is sized to fit within receptacletrays of standard dimensions for pallet truck, narrow aisle lift trucks,sit-down lift trucks and the like.

A method of converting an electric vehicle having a high peak power toaverage power ratio from electric power to hybrid power is alsodescribed. The method includes the steps of providing a hybrid powersupply apparatus as described above; removing a conventional batteryfrom the battery receptacle tray; positioning the housing of the hybridpower supply apparatus within the battery receptacle tray; andelectrically connecting the power output of the hybrid power supplyapparatus to the drive system of the vehicle.

The invention may also be employed in non-vehicular applications where ahybrid power supply is required for use in a relatively small,self-contained space. In the applicant's invention, the power outputlocated on the apparatus housing is preferably the only interfacebetween the apparatus and the load.

As should be apparent from the foregoing, it is an object of theinvention to provide a high energy density hybrid power supply systemthat is optimized for operation within an enclosure space similar totraditional removable battery systems, with identical electrical DCoutput, and having extended operational time between refueling stops.

A further object of the invention is to provide precise thermalregulation of the power supply components and safe and ergonomicexternal interfaces for ease of operator use.

Still another object is to replicate the traditional battery physicalcharacteristics, such as weight and enclosure size, so that the batteryreplacement procedure is transparent and safe for the vehicle operator.A related object is to reduce system vibrations to increase performanceof the hybrid system.

Another object is to provide a specialized chamber within the apparatushousing for temperature-controlled fuel storage.

A further object is to allow for fuel tank resizing to effectivelyincrease or decrease the range of the vehicle.

BRIEF DESCRIPTION OF DRAWINGS

In drawings which illustrate embodiments of the invention but whichshould not be construed as restricting the spirit or scope of theinvention in any way,

FIG. 1(a) is a rear isometric view of an electric lift truck showing aconventional prior art battery in its installed configuration.

FIG. 1(b) is an enlarged isometric view of the conventional battery ofFIG. 1(a).

FIG. 2 is a rear isometric view of the truck of FIG. 1 fitted with theapplicant's hybrid power supply apparatus.

FIG. 3 is an isometric view showing the general layout of theapplicant's hybrid power supply apparatus.

FIG. 4 is an isometric view of an alternative embodiment of theapparatus of FIG. 3 including weight counterbalancing and vibrationdamping features.

FIG. 5 is an isometric view showing the general layout of an alternativeembodiment of applicant's hybrid power generating apparatus including aninternally sealed temperature controlled fuel storage chamber.

FIG. 6 is a schematic diagram showing the hybrid fuel cell/batteryarchitecture and charging characteristics of the applicant's system.

FIG. 7 is an isometric view of one particular embodiment of theapplicant's hybrid power supply apparatus using liquid fuel and showingside panels of the apparatus housing in an open position to exposeinternal components.

FIG. 8 is a side elevational view of the embodiment of FIG. 7 with aside panel removed and showing exemplary air flow paths in dottedoutline.

FIG. 9 is an end isometric view of the embodiment of FIG. 7 showing theuser interface which is exposed in use.

FIG. 10 is a further isometric view of the embodiment of FIG. 7 showingthe side panels of the housing in a open position to expose internalcomponents.

FIG. 11 is an isometric view of an alternative embodiment of theinvention suitable for using compressed gas fuel.

FIG. 12 is a schematic drawing of one possible arrangement for aircooling of the applicant's hybrid power supply apparatus.

FIG. 13 is an isometric view of a further alternative embodiment of theinvention similar to the embodiment of FIG. 7 but configured as aGenset.

DESCRIPTION OF INVENTION

A conventional industrial or “traction” battery 10 for a forklift truck20 is shown in FIGS. 1(a) and 1(b). Battery 10 includes a box-shapedhousing 12 having opposed end faces 14, side faces 15 and top and bottomfaces 16. As shown in FIG. 1(a), truck 20 typically includes a main body22 mounted on wheels 24 and having a fork lift mechanism 26 attached.The main body 22 has a cavity or battery receptacle tray 28 which issized and shaped to removably receive one battery 10. In the exampleshown, tray 28 is rectangular in shape and is located in the center ofthe main vehicle body 22. However, the location and dimensions of tray28 will vary depending on the specific truck manufacturer, model andapplication. By way of example, pallet trucks have maximum allowablebattery tray dimensions of 31″ L×13″ W×32″ H (the height is variabledepending upon the battery capacity). Narrow aisle lift trucks vary to agreater extent, but a typical battery tray 28, for a 36 volt DC model,is 38″ L×20″ W×31″ H. A sit-down fork lift truck also has severalvariations, but a typical battery tray 28, for a 36 or 48 volt DC model,is 38″ L×32″ W×22″ H.

Battery 10 is enclosed to a greater or lesser extent depending on thelocation of battery tray 28 in truck 20. In the example shown in FIG.1(a), end faces 14 and a top face 16 are exposed. In other commonconfigurations only one end face 14 of housing 12 is exposed, theremainder being enclosed by the main truck body 22. Since battery 10 isextremely heavy (approximately 900 pounds in some applications), thebattery charging station and/or vehicle 20 may include a transportsystem (not shown) consisting of rollers and guides for ease of slidingthe battery 10 in and out of tray 28. The lift truck 20 or other vehiclemay also include standard mechanical retainers (not shown) to lock thebattery 10 in place within tray 28 for safety during operation.

The structure of conventional traction battery 10 is shown in greaterdetail in FIG. 1(b). Battery housing 12 is typically constructed fromsteel and includes a pair of lifting handles 17 mounted on opposed endfaces 14. A DC cable and plug interface 18 extends from housing 12 andis connected to the electrical drive system (not shown) of truck 20.Plug interface 18 is standard for most electric vehicles. A plurality ofbattery cells 19 are mounted within battery housing 12 as shown and areelectrically connected to the DC output plug interface 18. Battery 10 istypically of the lead acid type. When battery 10 requires recharging, itis usually manually rolled off truck 20 to a recharging station (notshown), a charged replacement battery 10 is rolled into tray 28, and theDC output plug 18 of the replacement battery 10 is connected to theelectrical drive system of truck 20. Depending upon the application,conventional batteries 10 have operating times as low as 4-5 hours andtherefore require frequent recharging. As discussed above, the frequentdaily removal of discharged batteries and substitution of fully chargedbatteries is labor-intensive and requires a costly inventory of sparebatteries. Of course, battery charging stations and associatedinstrumentation must also be provided.

The hybrid power supply apparatus 30 of the present invention isillustrated in its installed configuration on a truck 20 in FIG. 2. Asdiscussed further below, apparatus 30 is “hybrid” in character since itincludes both a fuel cell to generate electrical power and an energystorage means, such a storage battery, which is connectable to a load.Apparatus 30 has been engineered so that it is transparentlyinterchangeable with a conventional battery 10 in a “plug and play”manner without requiring any modification to truck 20. Moreparticularly, apparatus 30 has substantially the same shape, dimensions,weight and electrical interface as a battery 10 of FIGS. 1(a) and (b).This enables apparatus 30 to be easily inserted into or removed from anexisting battery tray 28 and used in the same manner as a conventionalbattery 10. However, apparatus 30 has performance characteristics,including an effective operating time, which are far superior to aconventional battery 10. By way of example, prototype apparatuses 30tested by the inventors have provided an order of magnitude greateroperating time before requiring refueling/recharging (i.e. up to 50hours compared to 4-8 hours for conventional batteries 10).

While hybrid fuel cell/battery power systems are of course well known inthe prior art, the integration of such a system within a small geometricspace (i.e. an enclosure capable of fitting within the dimensions of astandard battery tray 28) poses multiple design challenges. As describedin detail below, the various fuel cell hybrid components must beefficiently arranged within a small enclosure while maintaining weightcharacteristics and a DC interface similar or identical to conventionalbattery systems 10. Further, the placement of air inlets and outlets isimportant to avoid adding heat to truck 20 and for optimum internalthermal management. Accessibility of fuel inlets is similarly importantto ensure ease of refueling by operators.

Further, trucks 20 are designed for holding traction batteries 10 whichare very robust and insensitive to many environmental conditions. Fuelcell hybrid systems, by contrast, are much more sensitive totemperature, vibration, shock, debris, moisture and the like and hencethe applicant's invention has been engineered to address suchenvironmental factors, as discussed further below.

The general layout of the applicant's hybrid power supply apparatus 30is illustrated in FIG. 3. Apparatus 30 includes an external housing 32which encloses a hybrid power subsystem generally designated 34. Thevarious component parts and features of subsystem 34 are described indetail below. Housing 32 further includes an exposed end panel 36 whichis accessible when apparatus 30 is in use (i.e. corresponding to theexposed end face 14 of a conventional battery 10). Subsystem 34 ispreferably air-cooled. In the illustrated embodiment, an air inlet 38and an exhaust outlet 40 are located on housing panel 36. As discussedfurther below, hybrid apparatus 30 is configured to ensure that thetemperature of housing 32, and the exhaust expelled from outlet 40, iskept within safe limits to avoid operator injury. As shown in FIG. 4,air inlet 38 and outlet 40 may optionally be covered by a conventionalgrill or deflector shield 78 to filter debris and ensure the exhaust gasstream is ergonomically located for operator comfort.

A fuel inlet 42 is also provided on housing panel 36 for delivering fuelfrom a fuel source to hybrid power subsystem 34. In the illustratedembodiment, fuel inlet 42 is connectable to a fuel storage chamber 50located within housing 32. In use, fuel is delivered from storagechamber 50 to subsystem 34 to generate electrical power which isdelivered to a power output 44 connectable to a load, such as the drivesystem of a lift truck 20.

The housing 32 of FIGS. 2-5 is box-shaped to fit within the spaceconstraints of a conventional battery tray 28. However, as will beapparent to a person skilled in the art, housing 32 could be anygeometric shape provided that it is safely compatible with tray 28 andis ergonomically connectable to the vehicle electric drive system. Forexample, the electrical interfaces of power output 44 could be exposedat different locations to ergonomically mate with the electricalsub-system of the particular vehicle (or other load device) in question.

As mentioned above, the weight characteristics of applicant's apparatus30 preferably simulate a conventional battery 10 to avoid the need forvehicle modification. Hybrid power subsystem 34 is much lighter thanstandard lead acid batteries. Accordingly, for apparatus 30 to have amass similar to existing batteries 10, mass must be added. Such addedmass is essential as the counterbalance of many vehicles 20 is designedfor the heavy lead acid battery mass. As shown generally in FIG. 3,apparatus 30 may include a weight counterbalance 46 located withinhousing 32. As will be understood to a person skilled in the art,weights could alternatively be selectively added at various differentvoid locations within housing 32 to optimize counterbalance requirementsbased on the mass distribution of the hybrid power subsystem 34 and fuelstorage configurations. Housing 32 may also include a handle 37 for easeof transport (FIG. 4).

As mentioned above, hybrid power subsystem 34 is more sensitive tovibration and shock than conventional batteries 10. Accordingly,apparatus 30 also preferably includes vibration damping material 48located within housing 32. As shown in FIG. 4, damping material 48 maybe located, for example, immediately underneath hybrid power subsystem34 and underneath fuel storage chamber 50 in a lower portion of housing32. Closed cell foam or elastomeric materials such as sorbothane areexamples of suitable damping materials. Another possible embodimentincludes damping material specifically tuned to reduce coupling ofspecific vehicle vibrations and specific resonant frequencies ofapparatus 30 and enclosed subsystems. A further damping embodiment mayincorporate shock absorbing mechanical connectors, as known in the artfor use in vehicles, for internal mounting isolation of the hybrid powersubsystem 34. In yet another embodiment an external damping layer may beprovided positionable within receptacle tray 28 for supporting orattachment to housing 32. Preferably such an external damping layershould be constructed from a material that it is suitably rugged towithstand insertion and removal friction (for example, damping materialshaving a high sheer strength).

Hybrid power subsystem 34 may utilize various different types of liquid,compressed gas and hydride fuels. Suitable fuels include pure orenriched hydrogen gas, metal hydride, methanol, natural gas and propane(LPG). FIG. 5 illustrates the general layout of one embodiment of theinvention wherein the fuel storage chamber 50 is thermally isolated fromthe remainder of housing 32 by a baffle 52. In this embodiment, chamber50 would be suitable for holding a fuel source which should bemaintained at a particular temperature and pressure for optimumperformance (for example, LPG stored within a secured container 54).

FIG. 6 illustrates schematically the architecture of the hybrid powersubsystem 34 of apparatus 30 in further detail. Subsystem 34 includes afuel cell 60 which delivers raw DC current to a DC/DC converter 62. Anenergy storage device 64 is connected to the DC/DC converter 62 forstoring at least part of the conditioned DC current outputted byconverter 62. Energy storage device 64 may comprise, for example, abattery, a capacitor, or a combination thereof. Energy storage device 64is electrically coupled to a DC bus 66 for delivering electrical energyto a load 67, such as the drive system of a lift truck 20.

As explained above, hybrid power subsystem 34 may employ various typesof fuels. In preferred embodiments subsystem 34 uses readily availablefuels such as methanol and propane (LPG). In such cases, subsystem 34includes a fuel processor, such as a reformer 68, for converting rawfuel to substantially pure hydrogen or hydrogen-enriched gas suitablefor use by fuel cell 60. Reformer 68 is coupled to fuel storage chamber50 with suitable fuel lines. A fuel pump 69 may be provided fordelivering fuel from chamber 50 to reformer 68.

A computer controller 70 which receives input from various sensors, suchas voltage and current sensors 72, controls charging of storage device64 by fuel cell 60. As discussed further below, subsystem 34 alsoincludes fan blowers 74 for circulating air through flow paths withinhousing 32 to maintain the temperature of each component of apparatus 30within a preferred temperature range and to dilute exhaust gases priorto expulsion from housing 32. The operation of blowers 74 may also beregulated by controller 70.

As explained above, sudden load fluctuations are common-place in lifttrucks 20 and similar vehicles. Due to the slow response time ofreformer 68, a fuel cell system alone cannot respond quickly to rapidchanges in load and hence a hybrid system as exemplified by theapplicant's invention is desirable for such applications. Hybrid powersubsystem 34 is configured to maintain storage device 64 in a state ofhigh residual capacity to cope with load surges. This enables “ondemand” power to be supplied by storage device 64 while the power outputof fuel cell 60 can be varied independently to replenish energy tostorage device 64, or deliver power jointly to the load on anopportunistic basis. Moreover, the hybridization of subsystem 34 allowsfor the fuel cell 60 and reformer 68 components to be sized to meet onlythe average power requirements of the application (rather than the peakpower requirements). In the case of the duty cycle of an electric lifttruck 20, with characteristic peak power to average power ratios ofapproximately 10:1, this results in a significant reduction in thequantity of the higher priced fuel cell components of the system.

In use, hybrid power subsystem 34 is preferably configured so thatsensors 72 continuously monitor the state of charge and/or the voltageof storage device 64. When hybrid power apparatus 30 is subjected to aload, the state of charge of storage device 64 decreases as detected bysensors 72. In one embodiment of the invention, this information isprocessed by controller 70 which returns a feedback signal to fuel cell60 resulting in an increase in the fuel cell output charge current. In apreferred embodiment of the invention fuel cell 60 is not operated in aload-following mode. Rather, changes in the fuel cell charge current areminimized so that fuel cell 60 operates under near steady stateconditions for the bulk of its charging time to prolong its usefulservice life. This may be achieved by programming controller 70 to stepup or step down the fuel cell output charge only at discrete intervalsdepending upon the state of charge of storage device 64.

One representative embodiment of the applicant's hybrid power apparatus30 utilizing methanol fuel is illustrated in FIGS. 7-10. In thisembodiment, hybrid power apparatus 30 is illustrated with a top panel ofhousing 32 removed for clarity. Housing 32 also includes an end panel 80located opposite the end panel 36 having the user interfaces and a pairof side panels 82 and 84 which are pivotable between open and closedpositions (in FIGS. 7 and 10 side panels 82, 84 are shown in the openposition to expose the various components arranged within housing 32).

In the embodiment of FIGS. 7-10, fuel chamber 50 for storing methanolfuel is located in a bottom compartment of apparatus 30. Fuel inlet 42is located on exposed end panel 36 for supplying fuel to fuel chamber50. Storage device 64, such as a conventional battery, is positionedabove fuel chamber 50 proximate air inlet 38 (as shown best in FIG. 10).DC/DC power converter 62 is positioned adjacent storage device 64 in acentral portion of housing 32. Fuel cell 60 is positioned in an upperportion of housing 32 above storage device 64. Controller 70 is locatedadjacent fuel cell 60 at a location above DC/DC power converter 62. Asshown best in FIG. 10, power output 44 is coupled to DC bus 66 which isoperatively coupled to controller 70. A user control panel 85 isprovided on end panel 36 above fuel inlet 42 for monitoring andcontrolling operation of apparatus 30. For example, panel 85 may includea start/stop control button and a fuel level indicator.

The portion of housing 32 proximate end panel 80 is occupied principallyby reformer 68 which is connected by fuel line(s) to the underlying fuelstorage chamber 50 (FIG. 7). Reformer 68 may be housed within a shroud(not shown) to help dissipate radiant heat from reformer 68.

FIG. 11 illustrates another possible embodiment of the applicant'shybrid power supply apparatus 30 employing a compressed gas fuel (e.g.LPG) rather than liquid fuel. This embodiment of the invention isgenerally similar in layout to the embodiment of FIGS. 7-10, except thatfuel storage chamber 50 is located in an upper region of housing 32 andis thermally and hermetically isolated from the remainder of housing 32by means of wall 90. This enables the temperature and pressureconditions of chamber 50 to be modulated independently of the remainderof housing 32 to suit the requirements of the fuel source. Chamber 50 issized to receive a compressed gas tank 92 which may be either refillableor replaceable depending upon the choice of fuel. An access door havinga self-sealing hinge (not shown) may be provided for gaining access tochamber 50 to enable easy removal and replacement or examination of tank92. Alternatively, in the case of refillable tanks 92, a fuel inlet port(not shown) in fluid communication with tank 92 may be provided. As willbe apparent to a person skilled in the art, the size of fuel tank 92could easily be varied to effectively increase or decrease the range ofvehicle 20.

Sealed chamber 50 preferably includes a thermal sensor (not shown) andheating unit (not shown) connected to controller 70. The chambertemperature can thus be monitored and corrected for maintenance of aminimum temperature suitable for optimum operation of hybrid powersubsystem 34. The use of a sealed fuel storage chamber 50 also resultsin better regulation of fuel pressure and superior operation ofapparatus 30 in refrigerated environments. Further, a sealed chamber 50has the additional benefit of maintaining the cleanliness of hybridpower subsystem 34 which is located in a separate portion of housing 32and is not exposed to the environment when the chamber access door isopened for refueling etc.

In the embodiment of FIG. 11 fuel cell 60 is positioned immediatelyadjacent reformer 68 in a lower portion of housing 32 and controller 70is positioned above energy storage device 64 proximate housing surface36. Notwithstanding the different internal configuration, the embodimentof 11 functions in a manner similar to the embodiment of FIGS. 7-10described above. Other equivalent configurations could envisioned by aperson skilled in the art without departing from the invention.

As mentioned above, apparatus 30 is preferably air-cooled and includesblowers 74 for directing air flow within housing 32 (FIGS. 6 and 11).The various components of apparatus 30 are geometrically orderedrelative to air flow paths based on temperature limits and sensitivity.Preferably the coolant air is reused as much as possible to minimizetotal air flow. Since apparatus 30 is designed for low powerapplications, it is important to minimize flow impedances and electricalparasitic loads associated with the cooling system.

Optimum thermal regulation of hybrid power apparatus 30 is important forseveral reasons. Fuel cell systems, particularly those with associatedfuel processors, generate significant waste heat. In many cases hybridpower systems are operated outdoors or in applications having a fixedoutdoor exhaust (e.g. automobiles or home power systems). However, lifttrucks 20 and the like, which are often operated indoors, areconstrained to emit low temperature exhaust only. More particularly, itis important that the external surfaces of hybrid power apparatus 30,such as the exposed end panel 36 of housing 32, be maintained at a lowtemperature to avoid operator injury. Further, it is equally importantthat a significant amount of heat not be transferred from apparatus 30to the body 22 of truck 20 (i.e. all excess heat should preferably betransferred to the environment rather than placing additional thermalloads on associated equipment, such as truck 20). Optimum thermalregulation also enables hybrid power apparatus 30 to be used in a widerange of ambient temperatures typically serviced by trucks 20, includingsub-freezing refrigerated environments as would be encountered infreezer lockers and the like.

One particular arrangement for thermal management of apparatus 30 isillustrated generally in FIG. 7 and schematically in FIG. 12. A heattransfer gas, such as air, is circulated through apparatus 30 tomaintain the various components of hybrid power subsystem 34 withintheir optimum temperature ranges. The air is preferably moved throughdifferent flow paths between air inlet 38 and outlet 40. As shown inFIG. 12, a plurality of junctions 120 and adjustable valves 122 arepreferably provided for strategically dividing and merging the airstreams. In a normal operational mode (i.e. at normal ambienttemperatures) the incoming air passing through inlet 38 is divided intothree separate substreams 100, 102 and 104 at junctions 120. A firstsubstream 100 is initially passed over storage device 64 and DC/DC powerconverter 62. Both of the above components are sensitive to temperaturefluctuations and should be maintained at relatively cool operatingtemperatures for best performance. In the case of low ambienttemperatures, at least some of the inlet air may be pre-heated withheated exhaust air as discussed further below to protect storage device64 and converter 62 from excessively cold temperatures.

After passing over converter 62, the first substream 100 is divertedthrough a shroud surrounding reformer 68 to accept waste heat generatedby the reforming process. Reformers 68 typically operate at very hightemperatures (i.e. on the order of 600° C.). A first portion 100(a) ofsubstream 100 is then diverted to fuel cell 60 to maintain fuel cell 60at a desirable operating temperature (i.e. within the range ofapproximately 60-80° C.). A second portion 100(b) of substream 100bypasses fuel cell 60 and is used to dilute the exhaust stream asdescribed further below.

As illustrated in FIG. 12, the second and third substreams 102, 104 ofthe inlet air may be circulated directly to reformer 68 and fuel cell 60respectively. Second substream 102 is exhausted from reformer 68 at ahigh temperature and is merged with substream 104 at a junction 120located downstream from reformer 68. Substream 104 delivers oxident airto fuel cell 60 and contains water when expelled from fuel cell 60. Thehot air present in substream 102 evaporates the water content ofsubstream 104 and maintains the merged exhaust airstream in a vaporstate suitable for expulsion to the environment.

As shown in FIG. 12, a heat exchanger 124 is preferably provided to coolthe hydrogen gas generated by reformer 68 to ambient or near-ambienttemperature and to pre-heat the methanol fuel before the fuel is pumpedto reformer 68.

In the normal operational mode of the applicant's air cooling system,first portion 100(a) and second portion 100(b) of substream 100 arecombined with the exhaust stream (resulting from nixing of substreams102 and 104) at locations downstream from reformer 68. Portion 100(b),which is relatively cooler than portion 100(a) since it has not passedthrough fuel cell 60, reduces the temperature of the exhaust stream to asafe temperature (e.g. below 50° C.) before it is discharged throughoutlet 40. Substreams 100(a) and 100(b) also serve to dilute the carbonmonoxide content present in the exhaust stream prior to its expulsion tothe environment.

In an alternative operating mode suitable for low temperature operation,the first substream 100 is not divided into first and second portions100(a) and 100(b) (i.e. all of substream 100 passes through fuel cell60). In this embodiment, substream 100 may be subdivided downstream fromfuel cell 60 at an adjustable valve 122. A portion of substream 100 maybe recycled to pre-heat the incoming air drawn through outlet 38. Inthis case the inlet air may be divided into a further substream 106 formerging with the reformer exhaust (FIG. 12). An important feature ofthis arrangement is that the recycled portion of the heated air does notcontain any reformer exhaust gases.

The exemplary air flow patterns described above are preferably under thecontrol of microprocessor controller 70 which receives input fromvarious temperature and air flow sensors (not shown). In one embodimentof the invention, controller 70 may be programmed to periodicallyreverse the direction of air flow. This enables the periodic expulsionof built-up debris from the interior of housing 32 through air inlet 38.As indicated above, air inlet 38 and outlet 40 may also includeconventional grills or deflector shields 78 (FIG. 4) to filter debrisand ensure the exhaust gas stream is ergonomically located for operatorcomfort.

As will be apparent to a person skilled in the art, other equivalentmeans for flowing cooling gas streams through housing 32 may beenvisaged for the purposes of:

-   (1) Maintaining exhaust streams and operator interfaces at safe    temperatures and preventing transfer of thermal loads to other    equipment.-   (2) Maintaining various components of the hybrid power subsystem    within a preferred temperature range for optimum performance and    longevity.-   (3) Controlling the thermal status of different component parts    precisely and independently.-   (4) Enabling operation of electric vehicles at a wide range of    ambient temperatures-   (5) Dilution of exhaust gas constituents, such as carbon monoxide-   (6) Purging of waste materials-   (7) Minimizing parasitic electrical loads associated with the    cooling system for improved performance.

FIG. 13 illustrates a further alternative embodiment of the inventionsimilar to the embodiment of FIGS. 7-10, but configured as a portablegenset. In this embodiment, a standard AC electrical power outlet 126 isprovided rather than DC power output 44.

As should be apparent to a person skilled in the art, hybrid powersupply apparatus 30 is suitable for non-vehicular low power applicationswhere the size of the power supply is limited by size or geometricconstraints. For example, apparatus 30 may be used for on/off grid powergeneration, recreational power use, uninterruptable power supply andconventional battery replacement applications.

As will be apparent to those skilled in the art in the light of theforegoing disclosure, many alterations and modifications are possible inthe practice of this invention without departing from the spirit orscope thereof. Accordingly, the scope of the invention is to beconstrued in accordance with the substance defined by the followingclaims.

1. A hybrid power supply apparatus interchangeable with a conventionalbattery removably positionable within a battery receptacle tray of anelectric vehicle, the battery having a power output connectable to thedrive system of the vehicle, said hybrid power apparatus comprising: (a)a fuel cell; (b) an energy storage device chargeable by said fuel cell;(c) a housing enclosing said fuel cell and said energy storage device,wherein said housing is sized to fit within said battery receptacletray; and (d) a power output electrically connectable to said storagedevice and extending externally of said housing for electricallycoupling said apparatus to said drive system of said vehicle when saidhousing is positioned within said battery receptacle tray.
 2. Theapparatus of claim 1, further comprising a coolant system for flowinggas through said housing, said coolant system comprising: (a) a gasinlet for drawing gas into said housing; (b) at least one blowerpositioned within said housing for moving gas through said housing inpredetermined flow paths to regulate the temperature of said apparatus;and (c) a gas outlet for expelling exhaust gas from said housing.
 3. Theapparatus of claim 2, wherein said housing comprises a user interfacesurface which is exposed when said housing is placed within said vehiclereceptacle tray, wherein said gas inlet and gas outlet are located onsaid user interface surface.
 4. The apparatus of claim 3, wherein thetemperature of said exhaust gas does not exceed 50° C. when said coolantsystem is in operation.
 5. The apparatus of claim 3, wherein saidcoolant system maintains said user interface surface at a temperaturenot exceeding 50° C. when said apparatus is in operation.
 6. Theapparatus of claim 2, wherein said energy storage device is locatedwithin said housing proximate said gas inlet.
 7. The apparatus of claim1, further comprising a fuel processor positioned within said housingfor converting a source of fuel to hydrogen-enriched gas for delivery tosaid fuel cell.
 8. The apparatus of claim 7, further comprising a fuelstorage chamber located within said housing, wherein said storagechamber is in fluid communication with said fuel processor.
 9. Theapparatus of claim 8, further comprising a fuel inlet on said housing influid communication with said fuel storage chamber.
 10. The apparatus ofclaim 9, wherein said housing comprises a user interface surface whichis exposed when said housing is placed within said vehicle receptacletray, wherein said fuel inlet is located on said user interface surface.11. The apparatus of claim 8, wherein said fuel chamber is thermallyisolated from the remainder of said housing.
 12. The apparatus of claim1, further comprising a fuel storage chamber located within saidhousing, wherein said storage chamber is in fluid communication withsaid fuel cell.
 13. The apparatus of claim 8, wherein said fuel storagechamber stores menthanol fuel.
 14. The apparatus of claim 8, whereinsaid fuel storage chamber stores propane fuel.
 15. The apparatus ofclaim 1, further comprising a controller positioned within said housingfor regulating operation of said fuel cell depending upon the state ofcharge of said energy storage device.
 16. The apparatus of claim 1,wherein said energy storage device comprises at least one battery. 17.The apparatus of claim 1, wherein said energy storage device comprisesat least one capacitor.
 18. The apparatus of claim 1, further comprisinga DC/DC power converter positioned within said housing for converting DCcurrent generated by said fuel cell to a voltage suitable for chargingsaid energy storage device.
 19. The apparatus of claim 1, furthercomprising a load compensator positioned within said housing forincreasing the weight of said apparatus to a weight approximating theweight of said conventional battery.
 20. The apparatus of claim 1,further comprising a first vibration dampener positioned within saidhousing for absorbing vibration when said vehicle is in operation. 21.The apparatus of claim 20, comprising a second vibration dampener whichsurrounds at least part of said housing when said housing is positionedwithin said battery receptacle tray.
 22. The apparatus of claim 1,wherein said housing is sized to fit within a pallet truck batteryreceptacle tray having the following dimensions: 31″ L×13″ W×32″ H. 23.The apparatus of claim 1, wherein said housing is sized to fit within anarrow aisle lift truck battery receptacle tray having the followingdimensions: 38″ L×20″ W×31″ H.
 24. The apparatus of claim 1, whereinsaid housing is sized to fit within a sit-down lift truck batteryreceptacle tray having the following dimensions: 38″ L×32″ W×22″ H. 25.A method of converting an electric vehicle having a high peak power toaverage power ratio to hybrid power, the vehicle having a conventionalbattery removably positionable within a battery receptacle tray of thevehicle and electrically connectable to a drive system of the vehicle,said method comprising; (a) providing a hybrid power supply apparatus asdefined in claim 1; (b) removing said conventional battery from saidbattery receptacle tray; (c) positioning said housing of said hybridpower apparatus within said battery receptacle tray; and (d)electrically connecting said power output of said hybrid power apparatusto said drive system of said vehicle.
 26. A stand-alone hybrid powersupply apparatus comprising: (a) a fuel cell; (b) an energy storagedevice chargeable by said fuel cell; (c) a housing enclosing said fuelcell and said energy storage device within a self-contained space; and(d) a power output on an external surface of said housing forelectrically connecting said apparatus to a load, wherein said output isthe sole interface between said apparatus and said load.
 27. Theapparatus of claim 26, wherein said housing has a size not exceeding 38″L×32″ W×31″ H.
 28. A hybrid power apparatus for use in abattery-operated vehicle provided with an electrical receptacle and abattery receptacle tray, the hybrid power apparatus comprising; (a) ahybrid fuel cell subsystem including a fuel reformer, fuel cell, DCpower converter, microcontroller and energy storage device; (b) ahousing containing said hybrid fuel cell subsystem and having dimensionsless than said battery receptacle tray such that said housing is movablewithin said tray; (c) an external DC interface attached to said housingand electrically connected to said hybrid fuel cell subsystem andincluding a plug interface suitable to mate to said vehicle electricalreceptacle; and (d) gas inlet and outlet interfaces mounted on at leastone uncovered surface of said housing when said housing is placed withinsaid tray, wherein said interfaces are connected to said hybrid fuelcell subsystem and include circulation fans and valves connected to andcontrolled by said microcontroller of said hybrid fuel cell subsystem.